MC68HC08AZ16 Datasheet, PDF (182/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Serial Communications Interface Module (SCI)
Functional description
To locate the start bit, data recovery logic does an asynchronous
search for a ’0’ preceded by three ’1’s. When the falling edge of a
possible start bit occurs, the RT clock begins to count to 16.
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 4 summarizes the results of
the start bit verification samples.
Table 4. Start bit verification
RT3, RT5, and RT7 samples
000
001
010
011
100
101
110
111
Start bit verification
Yes
Yes
Yes
No
Yes
No
No
No
Noise flag
0
1
1
0
1
0
0
0
If start bit verification is not successful, the RT clock is reset and a
new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic
takes samples at RT8, RT9, and RT10. Table 5 summarizes the
results of the data bit samples.
13-sci
MOTOROLA
Serial Communications Interface Module (SCI)
MC68HC08AZ32
181